@mixin banxin {
    width: 1200px;
    margin: 0 auto;
}
@mixin sanjiao {
    display: inline-block;
    width: 9px;
    height: 6px;
    overflow: hidden;
    margin-left: 5px;
    // 小三角背景
    background: url(../img/xjt10.png) ;
}